Brake Upgrade - What Lies Beneath

We install a new brakes system on our '72 coupe

In my memory, I see the green eyes first: brilliant, piercing, and Bambi-height. Not just one pair, but a forest of them, signifying a flock, a herd, a bevy--whatever you call a group of a dozen or so deer spread out across a narrow roadway. It was about two in the morning, I had just finished putting the sway bars on the 454 '71 convertible I had pretensions of road racing, and I just couldn't stand to pack it in for the night without trying out the newly stiffened suspension.

Thus it was that I found myself zinging around a curve, high up in the mountains, into...that mess. I hit the brakes, and they let me down, as one caliper locked and I glanced off a buck with the passenger side of the chrome bumper. The good news is that the deer survived the experience, and so did the car. And I became tremendously interested in the subject of brakes.

To be fair, even C3 brakes are pretty good, especially considering the era. Even the early models came with cast-iron four-piston calipers, which means that each disc gets pinched between two pairs of pistons pressing toward one another from either side. There is, however, a better way, and we find that way with Wilwood's D8 calipers. Available in a variety of different colors, the D8 caliper comes in either the usual four-piston arrangement for front and rear, or with a six-piston front and four piston rear. In this case, we'll follow the installation of the latter setup on my '72 coupe, aka "Scarlett."

Better Binders...

Before we get to the install, let's talk about the differences between the Wilwoods and the stock calipers. The first is the added clamping force. While the size of the pad itself is basically the same, the greater surface area of the pistons behind it increases the force that squeezes the rotor. While my factory calipers were too dirty to get a precise reading, on the high side, the piston diameter measured around 1.41 inches. Going back to geometry class, we can figure the area by using the formula pie X r², or, as Wilwood expresses it in the instructions, (bore x bore) x 0.785 inch. Either equation works, and works out to a total area of 6.24 inches of clamping area for a stock front caliper. The D8-6, however, has a pair of 1.88-inch pistons, a pair measuring 1.38 inches, and a pair at 1.25 inches, which comes out to a total clamping area of 10.96 inches, for a gain of roughly 75 percent.

The rears are similar. The stock calipers have four pistons of around 0.925-inch in diameter, for a total clamping area of 2.68 inches. The Wilwood D8 rear calipers' four 1.125-inch pistons give a clamping area of 3.96 inches, for a gain of roughly 48 percent.

The other advantage is that, unlike the factory calipers, which are made of cast iron, the Wilwoods are made of aluminum, which drastically reduces weight where it matters most. Since calipers are part of the suspension that rides directly against the road, without being suspended by a spring, they're called "unsprung weight," which is a critical part of how the car handles. It's a simple matter of inertia: An object at rest wants to stay at rest, and the more mass it has, the more slowly it responds to any force placed upon it.

The goal of suspension is to keep the tires on the roadway, using the springs to account for differences in load and road surface. The lighter the assembly that the spring is pushing downwards, the more quickly it responds, since it doesn't have a lot of inertia holding it in place. It is, as we say, kind of a big deal--so much so that I've heard that in terms of handling, a reduction in unsprung weight is the equivalent to removing six times that much weight from the car itself.

With this in mind, consider that the front factory calipers weigh in at a cool 11.5 pounds each, and the rears weigh 12.2. The Wilwoods, on the other hand, come in at a svelte 6 pounds for the front and 6.3 at the rear, knocking nearly 23 pounds off the total unsprung weight, an average of 5.7 pounds per wheel.

Installing the calipers is as easy as any other brake job, with the addition of changing the master cylinder. For that we used an aluminum tandem unit from Wilwood, which itself is more than six pounds lighter than the stock cast-iron one. While Wilwood offers three bore sizes for its C3-compatible master cylinders (7?8-inch, 1 inch, and 11?8 inches) I requested the 11?8-inch version. Check out the accompanying captions for a full rundown of the installation process.

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Brake Upgrade - What Lies Beneath

Sometimes, the best things in life are subtle--such as Wilwood brake calipers hiding behind stock Rally wheels. The D8s pack 50-75 percent more clamping area than a stock caliper into an aluminum package that weighs about half as much.

Sometimes, the best things in life are subtle--such as Wilwood brake calipers hiding behind stock Rally wheels. The D8s pack 50-75 percent more clamping area than a stock caliper into an aluminum package that weighs about half as much.

1 We began by disconnecting the frame hard lines from the master cylinder so it could be removed. Keep the hard lines in their correct positions, as there is a front and a back line.

2 Once the lines are disconnected, undo the two bolts holding the master cylinder to the firewall and pull it off.

3 Now is a good time to check the pushrod length. If you need to adjust it, clamp the shaft in place and use a wrench to back it in or out as needed.

4 The stock cast-iron master cylinder is shown with the aluminum one from Wilwood. In addition to looking better, the Wilwood unit is more than 6 pounds lighter.

5 You'll need to install plugs on the right-side outlet holes of the master cylinder, and the fittings to accept the brake lines on the left. Pay attention to sizes, as the front and rear outlets require different–size fittings, and the kit comes with several.

6 Use lithium- or silicone-based grease on the threads and, using the included crush washers, torque the plugs and fittings down to 20-25 pounds each.

7 Using the bench-bleeder kit (included with our master cylinder), screw the plastic fittings into the outlets and attach the clear hoses, looping them over back into the master cylinder. The kit includes a handy clip to hold them in place.

8 Now for bench bleeding: Fill the master cylinder with brake fluid and use a screwdriver or similar tool to depress the piston in the cylinder until air bubbles no longer appear.

9 Once bled, install the master cylinder, making sure not to drip any brake fluid on your paint. Keeping the bench-bleeding lines in place will minimize the amount of fluid leaking out of the outlets while you're trying to get everything bolted into place. Torque the bolts to 24 pounds.

10 Now, on to the calipers. This is what we're replacing: a cast-iron four- piston unit that weighs 11.5 pounds. Remove the two 5/8-inch bolts holding it in place (one at the front, one at the rear, both on the other side of the caliper), unscrew the rubber brake hose from its fitting where it joins the hard line, and remove the clip holding it to it bracket.

11 Aside from the dramatic weight reduction, the advantage of the Wilwood caliper (top) is in its increased clamping force. In addition to having two more pistons, the D8-6 calipers have larger pistons, with 75 percent more clamping surface than a stock caliper.

12 Remove the sticker covering the brake-line inlet on the inboard side of the caliper, and screw in the elbow fitting included with the braided-steel brake-line kit. One end of the fitting has an AN thread, while the other has a tapered NPT thread. Screw the tapered end into the caliper and orient the AN side so the brake line can easily mate to it. When that's done, screw on the line.

13 If you're changing rotors, you'll need to do that now before reinstalling the calipers. After the initial installation, we upgraded ours to Wilwood’s drilled-and-slotted Polymatrix OE units.

14 The Wilwood rotors come in front- and rear-axle pairs, and are marked with an arrow to show which way they should turn.

15 Slip the rotor onto the wheel studs, and the caliper into its mounting position. After putting red Loctite on the caliper-mounting bolts, torque them to 70 pounds. Make sure the rotor is well seated before torquing the bolts, so it doesn't bind as you tighten things down.

16 With the front rotors and calipers in place, remove the C-clip that holds the brake-pad mounting pin in place and slide it out. Next, slide in the pads and replace the cross pin and clip.

17 Connect the caliper's braided-steel brake line to the frame hard line, using the included adapter fitting. If you've been letting the brake fluid run through the frame lines to flush them--which you should be--this is going to be a little messy. Be sure to wait until the fluid is running clear before connecting the lines.

18 While the rear Wilwood D8 calipers have the same piston count (four) as the stock ones, the pistons are bigger, giving the D8s about 48 percent more clamping area. They install the same as the fronts, except the caliper bolts should be torqued to 55 pounds instead of 70. Once they're installed, it's time to bleed the air out of the system.

19 Completely fill the master cylinder prior to bleeding. We used Wilwood's own 570 high-performance fluid.

20 Use the plastic lines from the bench-bleeder kit on the calipers; this will help keep fluid from squirting everywhere during the bleeding process. Start with the caliper farthest from the master cylinder and work your way in. Bleed only the top screws, and bleed the outboard screw first, then the inboard.

21 See the bubbles rising at the rear (right side) of the master cylinder? Bleed until those stop forming, and no more air comes out of the calipers. While fluid will not compress under pressure, air will, which means having air in your lines will cushion the force that the fluid would otherwise conduct to the brake calipers. This can result in both a soft pedal and less clamping force.

22 To test the decrease in stopping distance with the new brakes, we installed an Auto Meter D-PIC performance meter from Summit Racing.

23 Since no one makes a C3 Corvette A-pillar gauge pod, I used one from an '82-'92 F-body and modified it with a heat gun to fit my '72.

24 After using a file to clean up the round opening in the face of the gauge pod, the D-PIC slid right into place. Since the included gauge-mounting bracket was a little too long to fit in the pod—it was bearing against the A-pillar itself—I shortened it (and the brass screws) using a Dremel tool.

25 To wire up the D-PIC, I installed an inline 1-amp fuse holder and spliced into 12-volt positive power going to the fuel pump. I then grounded the D-PIC by splicing into a ground wire that went to the engine block, and tapped into the headlight circuit with the white dimmer wire.

26 Once everything was wired up and we knew it worked, it was time to permanently mount the gauge pod. While the instructions say to use screws to hold the pod in place, I used an emblem/trim adhesive for a cleaner look, and employed a pair of C-clamps to hold it in place while it cured.

27 Here's the finished product, mounted enough out of the way that it doesn't interfere with the driver's hands on the steering wheel. While the D-PIC comes in several different configurations, I chose the Ultra-Lite because of the silver rim and face, which will come close to matching the white-faced gauges I plan to install later.

28 With the dimmer wire installed, the D-PIC is substantially less bright once the headlights are on (as shown here), which keeps it from being distracting at night.

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